Pump assembly with uniform or programmed discharge

ABSTRACT

A pump assembly comprises a principal or first cylinder with a uniformly reciprocating first piston and a suction line and a pressure or exit line governed by valve means at the end of each piston stroke, and auxiliary or second cylinder having at most one-half of the capacity of the first cylinder and a uniformly reciprocating second piston cooperating with a connecting line leading into said pressure line. The second piston reciprocates in phase with but adversely to the first piston thus sucking a portion of liquid pressed by the first piston into the pressure line and on its return movement presses said liquidal portion into the common pressure line while the first piston sucks liquid into the first cylinder whereby a uniform or programmed movement of liquid in the pressure or exit line is insured.

United States Patent {72] Inventor Jiri Nina 14,186 2/1856 Dickerson et a1 103/213 X Prague, Czechoslovakia 595,942 12/1897 Dlehletal 103/6X [2]] A pl. No. 794,930 676,542 6/1901 Lultwieler 103/213 X [22] Filed Jan. 29,1969 1,375,200 4/1921 Barnickel 103/6 [45] Patented Aug.3, 1971 2,205,828 6/1940 Brown 103/168 [73] Assignee Ceskoshvensh akademie yeb 2,448,104 8/1948 Longenecker 103/168 Prague, Czechoslovakia 3,230,887 1/1966 Stallman 103/5 Priority 1968 Primary Examiner-Carlton R. Croyle 1 1 cmhoshvak Assistant ExaminerR. E. Glick 1 Pv Attorney-Paul H. Smolka ABSTRACT: A pump assembly comprises a principal or first [54] ggg gggfisggg g gigg on cylinder with a uniformly reciprocating first piston and a suc- 1 claim 1 Drama tion line and a pressure or exit line governed by valve means at g the end of each piston stroke, and auxiliary or second cylinder [52] 11.8. C1 417/265, h i a most one-half of the capacity of the first cylinder and 417/426 a uniformly reciprocating second piston cooperating with a ll". connecung [me lead ng "0 said pressure lme The second F041) 5/00, F04b 25/ 10 iston reciprocates in phase with but adversely to the first [50] Field ofSeareh 103/168,5, piston [hug sucking a portion of liquid pressed by the first 6.2l3,4;417/265 piston into the pressure line and on its return movement presses said liquidal portion into the common pressure line [56] Refemncescm while the first piston sucks liquid into the first cylinder UNITED STATES PATENTS whereby a uniform or programmed movement of liquid in the 2,172,103 9/1939 Kotaki l03/37A pre su e o exit line is insured.

32 l & i 3| Patented Aug. 3, 1971 3,597,114

INVENTOR Jiri Hrdi ATTORNEY L PUMP ASSEMBLY WITH UNIFORM OR PROGRAMMED DISCHARGE BACKGROUND OF THE INVENTION My invention relates to a pump assembly causing in its discharge or pressure tubing a uniform or a programmed periodical movement of a liquid. This requirement applies to many modern laboratory methods for example to automatic chromatographic analyzers wherein the flow of liquid has to be maintained at a highly accurate mean value and wherein pulsations of the work of the pump assembly have to be avoided or at least held at a minimum. This is important because said pulsations limit the mechanical properties of the material used as a charge in the column or the like, for example causing a progressing permanent deformation of the granulated charge.

It is already known to discharge a liquid in relatively uniform manner into columns from relatively large pump cylinders. A sufficiently uniform discharge requires however, a rather high rigidity of the pump assembly to preventjumps in the discharge. lf said rigidity is not sufficient, small jumps will arise in view of a temporal stoppage of the movement of the pistons until the resilient forces in the pump assembly reach a value overcoming the increased friction between the pump piston and the wall of its cylinder at the beginning of the movement. Another disadvantage of the beforesaid method lies in the necessity to refill the pump cylinder in each ofits repeated work cycles. This will result in an interruption of the supply of liquid into the column whether performed manually or automatically and is contrary to modern requirements in chromatographic installations necessitating a uniform fluidal flow through the columns.

In another known method one or more piston pumps, generally of the double-acting type, press the liquid simultaneously or alternately through a common discharge tubing. They work as a rule in periods of 5 to l0 seconds and each pump is governed by a special distributing device. As the discharges from the individual pistons alternate, the relevant tubings are switched over very quickly to a common exit piping by means of a special hydraulic switching device. These hydraulic switching devices are operated either mechanically by means of cams or by means of pnuematic servomotors which are equipped with a special distribution means for auxiliary pressure air. A substantial drawback of these pumps is their unusual mechanical complexity and the high requirements on accurate machining of cams, relatively large cylinders, pistons and the like. In some cases a special additional device is used for bridging over the period during which the delivery from individual cylinders is switched over so as to prevent any pronounced change in the pressure or the flow secured by the pump. This leads however, to a further increase of the complexity of the entire device.

SUMMARY OF THE INVENTION It is a general object of my invention to eliminate the abovementioned drawbacks of the known state of art.

A main feature of the invention resides in the fact that the uniform or freely programmed periodical movement of a liquid through at least one tubing, namely either a suction tubing or a discharge tubing, is secured by connecting at least one of the said tubings which are separated against the working space of a main pumping cylinder by a distribution member with a compensation cylinder the piston of which performs a periodical movement equal to the period of the piston of the main working pumping cylinder. The movement of the piston of the compensation pump is such that the liquid is supplied into the compensation pump, or that it is discharged in another part of the period into a common tubing, at a rate which just compensates the difference between the instantaneous value of a periodically changing transportation velocity of the liquid, insofar as it is produced by the main pumping cylinder, and the mean or programmed periodically changing value of the velocity of the movement of the liquid in the relevant tubing. In cases which are of primary practical importance the discharge from the pump has to be uniform. But in some cases it may be important that the movement in the suction tube of the pump or in both tubes be uniform. The most important case for practical purposes of the desired uniform discharge or displacement requires of course to provide in the above-mentioned manner a special compensation of the pulsations in the discharge tubing by means of a special compensation cylinder.

In addition to eliminating the above-mentioned substantial drawbacks of known pumps the advantage of the pump in accordance with the invention resides in the fact that for achieving a uniform movement in the suction or discharge tubing it is only required to connect thereto a compensation cylinder having a reciprocating piston but no distribution device such as valve means.

The pump in accordance with the invention can work with a long period -(for example some tens of seconds), but conveniently with a short period, for example 1 second or even less. With'short working periods it is possible to gain substantial advantages in that the pump may not only combine small dimensions with a high accuracy and high pressures, but in addition the necessary regularities of the discharge are achieved by very simple means. Any residual error resulting from inaccuracies of machining of driving means such as cams and the like has then an uncomparably smaller efi'ect than in known types of pumps with long periods. In the case of relatively small and high-speed pumps any inaccuracies have such short duration in comparison with an absolutely regular discharge that they may be better tolerated than could be the case in known types of pumps with a long working period. Any irregularities in pumps in accordance with the invention are manifested by so short variations about the central value of the transflux that as a rule, they completely disappear already in view of the resilience of the walls of the employed device and of the columns themselves and particularly in the case of the usual application of a manometer. The plasticity of the usual types of manometers represents by itself a sufficiently large resilient capacity which in the overall connection becomes effective in combination with the resistance of the column as a filter of relatively high frequency variations, so that even without the use of any additional dampers of pulsations a sufficiently regular discharge is achieved even if the mechanism comprises irregularities which could not be tolerated in known types of pumps. But this does not mean that in the pump in accordance with the invention the existence of such irregularities would have to be considered. On the contrary, with the same accuracy of the cams it is possible for the above-mentioned reasons, particularly at higher speeds of the pump in accordance with the invention, to better achieve uniform rates of flow which lie below admissible tolerances of irregularities of absolutely uniform transflux or rate of flow.

DESCRIPTION OF THE DRAWING The said and other objects of my invention 'will be more fully understood from the following specification when read with the accompanying drawing in which one embodiment is schematically illustrated in a side view partly in cross section.

DETAILED DESCRIPTION My new device as shown comprises two pump cylinders namely a principal or first cylinder 11 and an auxiliary or second cylinder 21 which may be arranged in parallel possibly in a common block 10. In each cylinder reciprocates with uniform speed a plunger 12 and 22, each of which is operated by proper driving means such as by a connecting rod 13 or 23 linked to an arm of a swingably mounted double lever 14 or 24, its other arm bearing rollers 15 or 25 actuated by cams 16 or 26 mounted on rotatable shafts l7 and 27 which possibly can be united. A permanent contact between rollers 15, 25 and cams 16, 26 is insured by the springs 18, 28.

The plungers 12, 22 move with uniform speed in cylinders 11, 21 in identical periods but in mutually adverse directions so that one plunger sucks material in while the other pushes material out, and vice versa. In order to insure a uniform movement of the liquid through the exit line 33 the volumetric work of plunger 22 will be substantially one-half of that of plunger 12 by diminishing namely substantially halving either its stroke or its diameter in relation to plunger 12.

Plunger l2 sucks material into cylinder 11 through inlet line 34 and presses it out therefrom through the outlet lines 31, 33, said lines 31 and 34 being governed by the valve member 30. The auxiliary or second cylinder 21 is connected to the outlet line 31 by line 32 which alternately serves as inlet or suction line and as outlet or pressure line therefor.

The valve member 30 is operated by the jointed levers 35, 36 which are actuated by the arm 38 ofa three-armed lever 37 turnable over the stationary pin 40 and bearing rollers 41 on its shorter arms 39. These rollers are alternately displaced by the cam 42 which either rotates with shaft 17 or is at least timely coordinated with cam 16.

The device operates as follows:

As shown in the drawing plunger 12 is in its lowest position at the beginning of the pressure stroke and plunger 13 in its highest position at the beginning of its suction stroke. The valve member 30 connects the principal cylinder 11 over the tubular section 31 to the exit or pressure line 33 and over the continuing section 32 with the auxiliary cylinder 21. While plunger 12 moves upward to press material formerly sucked into cylinder 11 through section 31 into the exit line 33, a portion of said material for example one-half thereof is sucked by the downwardly moving plunger 22 through tubular section 32 into cylinder 21. At the ends of these strokes the valve member 30 is turned to connect cylinder 11 with the inlet line 34 so that the downwardly moving plunger 12 again sucks material into cylinder 11. Simultaneously the upwardly moving plunger 22 presses the precedingly sucked-in material through tubular section 32 into the exit line 33 thereby assuring a programmed or constant flow therethrough.

The earns 17, 27 and 42 may be exchangeable against other similarly cooperating cams to provide other strokes to pistons 12 and 22 and thus to change the programmed flow through the common outlet tubing 33.

While I have shown and described a specific embodiment of my invention to illustrate the application of its principles, it

will be understood that it may be otherwise embodied without departing from such principles.

What I claim as my invention is:

1. A small capacity uniform discharge rate pump assembly comprising a first pump and a second pump, each of said pumps having a reciprocating piston in a cylinder and a port communicating with the interior of said cylinder, said pump assembly including an inlet passage and an outlet passage and rotaryvalve means, first means for conducting fluid between said inlet passage and said valve means, second means for conducting fluid between said valve means and said second pump port, said outlet passage communicating with said second fluid-conducting means said first pump port communicating with said valve means, said rotary valve means including a rotary valve element having an interior passage having an inlet and outlet spaced from each other around the circumference of said valve element, said passage being arranged for communicating exclusively between said first conducting means and said first pump port in a first rotary position and exclusively between said second conducting means and said first pump port in a second rotary position, said first conducting means communicating with said valve means on the opposite side of said pump port from said second conducting means, said first and second conducting means having substantially equal angular spacing from said pump port for mutually exclusive alternate alignment with said passage inlet and outlet upon equal rotation of said valve element in opposite directions with respect to said first pump port, and means for intermittently rotating said valve element between said first and second ositions, said pistons of said first and second pump means emg movable in mutually opposite directions, said second pump means having a volumetric working capacity of substantially one-half of the volumetric working capacity of said first pump means, said first and second pump means operating in timed relation with movement of said rotary valve element between said first and second positions, said second pump means drawing onehalf of the fluid discharge of said first pump means during the suction stroke of said second pump means, said second pump means discharging through said outlet passage fluid drawn during the preceding suction stroke, whereby fluid is pumped through said outlet passage alternately from said first pump means and said second pump means at a substantially uniform rate. 

1. A small capacity uniform discharge rate pump assembly comprising a first pump and a second pump, each of said pumps having a reciprocating piston in a cylinder and a port communicating with the interior of said cylinder, said pump assembly including an inlet passage and an outlet passage and rotary valve means, first means for conducting fluid between said inlet passage and said valve means, second means for conducting fluid between said valve means and said second pump port, said outlet passage communicating with said second fluid-conducting means said first pump port communicating with said valve means, said rotary valve means including a rotary valve element having an interior passage having an inlet and outlet spaced from each other around the circumference of said valve element, said passage being arranged for communicating exclusively between said first conducting means and said first pump port in a first rotary position and exclusively between said second conducting means and said first pump port in a second rotary position, said first conducting means communicating with said valve means on the opposite side of said pump port from said second conducting means, said first and second conducting means having substantially equal angular spacing from said pump port for mutually exclusive alternate alignment with said passage inlet and outlet upon equal rotation of said valve element in opposite directions with respect to said first pump port, and means for intermittently rotating said valve element between said first and second positions, said pistons of said first and second pump means being movable in mutually opposite directions, said second pump means having a volumetric working capacity of substantially one-half of the volumetric working capacity of said first pump means, said first and second pump means operating in timed relation with movement of said rotary valve element between said first and second positions, said second pump means drawing onehalf of the fluid discharge of said first pump means during the suction stroke of said second pump means, said second pump means discharging through said outlet passage fluid drawn during the preceding suction stroke, whereby fluid is pumped through said outlet passage alternately from said first pump means and said second pump means at a substantially uniform rate. 